Methods for transmitting and receiving reference signals in wireless communication system, and devices for same

ABSTRACT

This method for a transmitting side to transmit reference signals in a wireless communication system may comprise the step of: generating first reference signals for the demodulation of control channels and second reference signals for the demodulation of data channels; overlapping mapping the first and second reference signals to resources to which the control channels have been allocated in a predefined subframe; and transmitting the first and second reference signals mapped to the resources to which the control channels have been allocated.

TECHNICAL FIELD

The present invention relates to a wireless communication system, andmore particularly, to a method of transmitting and receiving a referencesignal in a wireless communication system and an apparatus therefor.

BACKGROUND ART

3GPP LTE (3rd Generation Partnership Project Long Term Evolution) systemis designed with a frame structure having a TTI (transmission timeinterval) of 1 ms and data requirement latency time for a videoapplication is 10 ms. Yet, with the advent of a new application such asreal-time control and tactile internet, 5G technology in the futurerequires data transmission of lower latency and it is anticipated that5G data requirement latency time is going to be lowered to 1 ms.

However, the legacy frame structure of 1 ms TTI is unable to satisfy the1 ms data requirement latency. 5G aims to provide data latency reducedas much as 10 times compared to the legacy data latency.

Although 5G communication system requires a new frame structure to solvethe abovementioned problem, the new frame structure has not beenproposed yet.

DISCLOSURE OF THE INVENTION Technical Tasks

A technical task of the present invention is to provide a method for atransmitting side to transmit a reference signal in a wirelesscommunication system.

Another technical task of the present invention is to provide a methodfor a receiving side to receive a reference signal in a wirelesscommunication system.

Another technical task of the present invention is to provide atransmission device for transmitting a reference signal in a wirelesscommunication system.

The other technical task of the present invention is to provide areception device for receiving a reference signal in a wirelesscommunication system.

Technical tasks obtainable from the present invention are non-limitedthe above-mentioned technical task. And, other unmentioned technicaltasks can be clearly understood from the following description by thosehaving ordinary skill in the technical field to which the presentinvention pertains.

Technical Solution

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described, accordingto one embodiment, a method of transmitting a reference signal, by atransmitting side, in a wireless communication system, includesgenerating first reference signals for demodulating a control channeland second reference signals for demodulating a data channel, mappingthe first reference signals and the second reference signals to aresource of a predefined subframe to which a control channel is assignedby overlapping the first reference signals and the second referencesignals, and transmitting the first reference signals and the secondreference signals mapped to the resource to which the control channel isassigned. Predefined cyclic shift values can be applied to the firstreference signals and the second reference signals. Different cyclicshift value can be applied to the first reference signals and the secondreference signals. When two values have a greatest difference amongpredefined cyclic shift values, one of the two values is applied to thefirst reference signals and another can be applied to the secondreference signals. The resource to which the control channel is assignedcan include a first symbol, a second symbol, a fourth symbol, or aimmediately preceding symbol of a last symbol in the predefinedsubframe. The mapping may further include mapping the first referencesignals and the second reference signals to whole band of the resourceto which the control channel is assigned.

To further achieve these and other advantages and in accordance with thepurpose of the present invention, according to a different embodiment, amethod of receiving a reference signal, by a receiving side, in awireless communication system, includes receiving first referencesignals for demodulating a control channel and second reference signalsfor demodulating a data channel in a resource to which a control channelis assigned, detecting control information using the first referencesignals, and detecting data using the control information and the secondreference signals. The first reference signals and the second referencesignals can be received in a manner of being overlapped and mapped tothe resource to which the control channel is assigned. The firstreference signals and the second reference signals can be received in amanner of being mapped to whole band of the resource to which thecontrol channel is assigned. Predefined cyclic shift values can beapplied to the first reference signals and the second reference signals.Different cyclic shift value can be applied to the first referencesignals and the second reference signals. When two values have agreatest difference among predefined cyclic shift values, one of the twovalues is applied to the first reference signals and another can beapplied to the second reference signals. The resource to which thecontrol channel is assigned can include a first symbol, a second symbol,a fourth symbol, or a immediately preceding symbol of last symbol in thepredefined subframe.

To further achieve these and other advantages and in accordance with thepurpose of the present invention, according to a further differentembodiment, a transmitting apparatus for transmitting a reference signalin a wireless communication system includes a processor configured togenerate first reference signals for demodulating a control channel andsecond reference signals for demodulating a data channel, the processorconfigured to map the first reference signals and the second referencesignals to a resource of a predefined subframe to which a controlchannel is assigned by overlapping the first reference signals and thesecond reference signals, and a transmitter configured to transmit thefirst reference signals and the second reference signals mapped to theresource to which the control channel is assigned.

To further achieve these and other advantages and in accordance with thepurpose of the present invention, according to a further differentembodiment, a receiving apparatus for receiving a reference signal in awireless communication system includes a receiver configured to receivefirst reference signals for demodulating a control channel and secondreference signals for demodulating a data channel in a resource to whicha control channel is assigned, and a processor configured to detectcontrol information using the first reference signals, the processorconfigured to detect data using the control information and the secondreference signals.

Advantageous Effects

According to a frame structure provided by the present invention, it isable to achieve low latency (i.e., OTA (w/initiation)<1 ms)corresponding to 5G service requirement and provide DL/UL flexibilitycapable of efficiently supporting asymmetry of DL/UL traffic as much aspossible.

According to one embodiment, it is able to reduce waste of RS resourcesfor detecting a data channel and a control channel in a self-containedframe structure and reduce decoding latency.

Effects obtainable from the present invention may be non-limited by theabove mentioned effect. And, other unmentioned effects can be clearlyunderstood from the following description by those having ordinary skillin the technical field to which the present invention pertains.

DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiment(s) of the invention andtogether with the description serve to explain the principle of theinvention.

FIG. 1 is a block diagram for configurations of a base station 105 and auser equipment 110 in a wireless communication system 100;

FIG. 2 is a diagram for explaining correlation between IMT 2020 coreperformance requirement for 5G and 5G performance requirement perservice scenario;

FIG. 3 is a diagram for LTE/LTE-A frame structure;

FIG. 4 is a diagram for an example of FDD/TDD frame structure inLTE/LTE-A system;

FIG. 5 is a diagram for an example of a self-contained subframestructure;

FIG. 6 is a diagram for a HARQ procedure when a UL resource of a datazone is immediately allocated;

FIG. 7 is a diagram for a HARQ procedure when a UL resource of a datazone is not immediately allocated;

FIG. 8 is a diagram for a new frame structure according to a proposal1-1 of the present invention;

FIG. 9 is a diagram for explaining a case that DL transmission timing isoverlapped with UL transmission timing;

FIG. 10 is a diagram illustrating an example that a DL data symbolboundary is not matched with a UL data symbol boundary in a data zone ina base station;

FIG. 11 is a diagram illustrating an example of an RF structure of atransceiver of a base station;

FIG. 12 is a diagram illustrating an example of a frame structuretime-frequency resource on a TDD carrier;

FIG. 13 is a diagram illustrating an example of a frame structuretime-frequency resource on a FDD carrier;

FIG. 14a is a diagram for an example of an RS assignment pattern when aresource region for DL/UL flexibility is allocated via a DL data channelin a self-contained subframe and FIG. 14b is a diagram for an example ofan RS assignment pattern when a resource region for DL/UL flexibility isallocated via a UL data channel in a self-contained subframe;

FIG. 15a is a diagram for an example of an RS assignment pattern when aresource region for DL/UL flexibility is allocated via a DL data channelin a self-contained subframe and FIG. 15b is a diagram for an example ofan RS assignment pattern when a resource region for DL/UL flexibility isallocated via a UL data channel in a self-contained subframe;

FIG. 16 is a diagram for a method of securing orthogonality between C_RSand D_RS when a data region is allocated to a DL data region in aself-contained subframe structure;

FIG. 17 is a diagram for explaining a case that a control channel isused for the whole band and a data channel is used for 24^(th) RB and2^(nd) RB among 25 RBs in total.

BEST MODE Mode For Invention

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. In the following detailed description of the inventionincludes details to help the full understanding of the presentinvention. Yet, it is apparent to those skilled in the art that thepresent invention can be implemented without these details. Forinstance, although the following descriptions are made in detail on theassumption that a mobile communication system includes 3GPP LTE system,the following descriptions are applicable to other random mobilecommunication systems in a manner of excluding unique features of the3GPP LTE.

Occasionally, to prevent the present invention from getting vaguer,structures and/or devices known to the public are skipped or can berepresented as block diagrams centering on the core functions of thestructures and/or devices. Wherever possible, the same reference numberswill be used throughout the drawings to refer to the same or like parts.

Besides, in the following description, assume that a terminal is acommon name of such a mobile or fixed user stage device as a userequipment (UE), a mobile station (MS), an advanced mobile station (AMS)and the like. And, assume that a base station (BS) is a common name ofsuch a random node of a network stage communicating with a terminal as aNode B (NB), an eNode B (eNB), an access point (AP) and the like.Although the present specification is described based on IEEE 802.16msystem, contents of the present invention may be applicable to variouskinds of other communication systems.

In a mobile communication system, a user equipment is able to receiveinformation in downlink and is able to transmit information in uplink aswell. Information transmitted or received by the user equipment node mayinclude various kinds of data and control information. In accordancewith types and usages of the information transmitted or received by theuser equipment, various physical channels may exist.

The following descriptions are usable for various wireless accesssystems including CDMA (code division multiple access), FDMA (frequencydivision multiple access), TDMA (time division multiple access), OFDMA(orthogonal frequency division multiple access), SC-FDMA (single carrierfrequency division multiple access) and the like. CDMA can beimplemented by such a radio technology as UTRA (universal terrestrialradio access), CDMA 2000 and the like. TDMA can be implemented with sucha radio technology as GSM/GPRS/EDGE (Global System for Mobilecommunications)/General Packet Radio Service/Enhanced Data Rates for GSMEvolution). OFDMA can be implemented with such a radio technology asIEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, E-UTRA (EvolvedUTRA), etc. UTRA is a part of UMTS (Universal Mobile TelecommunicationsSystem). 3GPP (3rd Generation Partnership Project) LTE (long termevolution) is a part of E-UMTS (Evolved UMTS) that uses E-UTRA. The 3GPPLTE employs OFDMA in DL and SC-FDMA in UL. And, LTE-A (LTE-Advanced) isan evolved version of 3GPP LTE.

Moreover, in the following description, specific terminologies areprovided to help the understanding of the present invention. And, theuse of the specific terminology can be modified into another form withinthe scope of the technical idea of the present invention.

In case of performing wireless transmission between a base station and aUE, a transmission to the UE from the base station is commonly referredto as a DL transmission and a transmission to the base station from theUE is commonly referred to as a UL transmission. A scheme of determininga radio resource between the DL transmission and the UL transmission isdefined as duplex. When a frequency band is divided into a DLtransmission band and a UL transmission band and transmission andreception are performed in both directions, it is referred to asfrequency division duplex (FDD).

FIG. 1 is a block diagram for configurations of a base station 105 and auser equipment 110 in a wireless communication system 100.

Although one base station 105 and one user equipment 110 (D2D userequipment included) are shown in the drawing to schematically representa wireless communication system 100, the wireless communication system100 may include at least one base station and/or at least one userequipment.

Referring to FIG. 1, a base station 105 may include a transmitted (Tx)data processor 115, a symbol modulator 120, a transmitter 125, atransceiving antenna 130, a processor 180, a memory 185, a receiver 190,a symbol demodulator 195 and a received data processor 197. And, a userequipment 110 may include a transmitted (Tx) data processor 165, asymbol modulator 170, a transmitter 175, a transceiving antenna 135, aprocessor 155, a memory 160, a receiver 140, a symbol demodulator 155and a received data processor 150. Although the base station/userequipment 105/110 includes one antenna 130/135 in the drawing, each ofthe base station 105 and the user equipment 110 includes a plurality ofantennas. Therefore, each of the base station 105 and the user equipment110 of the present invention supports an MIMO (multiple input multipleoutput) system. And, the base station 105 according to the presentinvention may support both SU-MIMO (single user-MIMO) and MU-MIMO (multiuser-MIMO) systems.

In downlink, the transmission data processor 115 receives traffic data,codes the received traffic data by formatting the received traffic data,interleaves the coded traffic data, modulates (or symbol maps) theinterleaved data, and then provides modulated symbols (data symbols).The symbol modulator 120 provides a stream of symbols by receiving andprocessing the data symbols and pilot symbols.

The symbol modulator 120 multiplexes the data and pilot symbols togetherand then transmits the multiplexed symbols to the transmitter 125. Indoing so, each of the transmitted symbols may include the data symbol,the pilot symbol or a signal value of zero. In each symbol duration,pilot symbols may be contiguously transmitted. In doing so, the pilotsymbols may include symbols of frequency division multiplexing (FDM),orthogonal frequency division multiplexing (OFDM), or code divisionmultiplexing (CDM).

The transmitter 125 receives the stream of the symbols, converts thereceived stream to at least one or more analog signals, additionallyadjusts the analog signals (e.g., amplification, filtering, frequencyupconverting), and then generates a downlink signal suitable for atransmission on a radio channel. Subsequently, the downlink signal istransmitted to the user equipment via the antenna 130.

In the configuration of the user equipment 110, the receiving antenna135 receives the downlink signal from the base station and then providesthe received signal to the receiver 140. The receiver 140 adjusts thereceived signal (e.g., filtering, amplification and frequencydownconverting), digitizes the adjusted signal, and then obtainssamples. The symbol demodulator 145 demodulates the received pilotsymbols and then provides them to the processor 155 for channelestimation.

The symbol demodulator 145 receives a frequency response estimated valuefor downlink from the processor 155, performs data demodulation on thereceived data symbols, obtains data symbol estimated values (i.e.,estimated values of the transmitted data symbols), and then provides thedata symbols estimated values to the received (Rx) data processor 150.The received data processor 150 reconstructs the transmitted trafficdata by performing demodulation (i.e., symbol demapping, deinterleavingand decoding) on the data symbol estimated values.

The processing by the symbol demodulator 145 and the processing by thereceived data processor 150 are complementary to the processing by thesymbol modulator 120 and the processing by the transmission dataprocessor 115 in the base station 105, respectively.

In the user equipment 110 in uplink, the transmission data processor 165processes the traffic data and then provides data symbols. The symbolmodulator 170 receives the data symbols, multiplexes the received datasymbols, performs modulation on the multiplexed symbols, and thenprovides a stream of the symbols to the transmitter 175. The transmitter175 receives the stream of the symbols, processes the received stream,and generates an uplink signal. This uplink signal is then transmittedto the base station 105 via the antenna 135.

In the base station 105, the uplink signal is received from the userequipment 110 via the antenna 130. The receiver 190 processes thereceived uplink signal and then obtains samples. Subsequently, thesymbol demodulator 195 processes the samples and then provides pilotsymbols received in uplink and a data symbol estimated value. Thereceived data processor 197 processes the data symbol estimated valueand then reconstructs the traffic data transmitted from the userequipment 110.

The processor 155/180 of the user equipment/base station 110/105 directsoperations (e.g., control, adjustment, management, etc.) of the userequipment/base station 110/105. The processor 155/180 may be connectedto the memory unit 160/185 configured to store program codes and data.The memory 160/185 is connected to the processor 155/180 to storeoperating systems, applications and general files.

The processor 155/180 may be called one of a controller, amicrocontroller, a microprocessor, a microcomputer and the like. And,the processor 155/180 may be implemented using hardware, firmware,software and/or any combinations thereof. In the implementation byhardware, the processor 155/180 may be provided with such a deviceconfigured to implement the present invention as ASICs (applicationspecific integrated circuits), DSPs (digital signal processors), DSPDs(digital signal processing devices), PLDs (programmable logic devices),FPGAs (field programmable gate arrays), and the like.

Meanwhile, in case of implementing the embodiments of the presentinvention using firmware or software, the firmware or software may beconfigured to include modules, procedures, and/or functions forperforming the above-explained functions or operations of the presentinvention. And, the firmware or software configured to implement thepresent invention is loaded in the processor 155/180 or saved in thememory 160/185 to be driven by the processor 155/180.

Layers of a radio protocol between a user equipment/base station and awireless communication system (network) may be classified into 1st layerL1, 2nd layer L2 and 3rd layer L3 based on 3 lower layers of OSI (opensystem interconnection) model well known to communication systems. Aphysical layer belongs to the 1st layer and provides an informationtransfer service via a physical channel. RRC (radio resource control)layer belongs to the 3rd layer and provides control radio resourcedbetween UE and network. A user equipment and a base station may be ableto exchange RRC messages with each other through a wirelesscommunication network and RRC layers.

In the present specification, although the processor 155/180 of the userequipment/base station performs an operation of processing signals anddata except a function for the user equipment/base station 110/105 toreceive or transmit a signal, for clarity, the processors 155 and 180will not be mentioned in the following description specifically. In thefollowing description, the processor 155/180 can be regarded asperforming a series of operations such as a data processing and the likeexcept a function of receiving or transmitting a signal without beingspecially mentioned.

The present invention proposes new and various frame structures for a5^(th) generation (5G) communication system. In a next generation 5Gsystem, scenarios can be classified into Enhanced Mobile BroadBand(eMBB), Ultra-reliable Machine-Type Communications (uMTC), MassiveMachine-Type Communications (mMTC), and the like. The eMBB correspondsto a next generation mobile communication scenario having such acharacteristic as high spectrum efficiency, high user experienced datarate, high peak data rate, and the like, the uMTC corresponds to a nextgeneration mobile communication scenario having such a characteristic asultra-reliable, ultra-low latency, ultra-high availability, and the like(e.g., V2X, Emergency Service, Remote Control), and the mMTC correspondsto a next generation mobile communication scenario having such acharacteristic as low cost, low energy, short packet, and massiveconnectivity (e.g., IoT).

FIG. 2 is a diagram for explaining correlation between IMT 2020 coreperformance requirement for 5G and 5G performance requirement perservice scenario.

FIG. 2 illustrates correlation between core performance requirement for5G proposed by IMT 2020 and 5G performance requirement per servicescenario.

In particular, uMTC service has very high restriction on Over The Air(OTA) Latency Requirement and requires high mobility and highreliability (OTA Latency: <1 ms, Mobility: >500 km/h, BLER: <10⁻⁶).

FIG. 3 is a diagram for LTE/LTE-A frame structure.

FIG. 3 shows a basic concept of a frame structure of LTE/LTE-A. Oneframe corresponds to 10 ms and includes 10 1-ms subframes. One subframeincludes 2 0.5-ms slots and one slot includes 7 OFDM (OrthogonalFrequency Division Multiplexing) symbols. One resource block (RB) isdefined by 12 subcarriers each of which has 15 kHz space and 7 OFDMsymbols. A base station delivers a primary synchronization signal (PSS)and a secondary synchronization signal (SSS) for synchronization aphysical broadcast channel (PBCH) for system information in a centerfrequency (6 RBs). In this case, it may have a difference in the framestructure and positions of the signal and the channel depending on anormal/extended CP (cyclic prefix) and TDD (Time Division Duplex)/FDD(Frequency Division Duplex).

FIG. 4 is a diagram for an example of FDD/TDD frame structure inLTE/LTE-A system.

Referring to FIG. 4, in case of a FDD frame structure, a downlinkfrequency band is distinguished from an uplink frequency band. In caseof a TDD frame structure, a downlink region is distinguished from anuplink region in a subframe unit in the same band.

FIG. 5 is a diagram for an example of a self-contained subframestructure.

FIG. 5 illustrates a self-contained subframe structure which is proposedto satisfy a low-latency requirement among 5G performance requirements.A TDD-based self-contained subframe structure has a resource section fordownlink, a resource section for uplink (e.g., a downlink controlchannel and an uplink control channel), a guard period (GP) for solvingan interference issue between downlink and uplink, and a resourcesection for data transmission in a single subframe.

FIG. 5(a) shows an example of a self-contained subframe structure. Asubframe is configured in an order of a resource section for downlink, aresource section for uplink, and a resource section for data and a GPexists between the resource sections. In FIG. 5(a), a downlink resourcesection represented as DL may correspond to a resource section for adownlink control channel and an uplink resource section represented asUL may correspond to a resource section for an uplink control channel

FIG. 5(b) shows a different example of a self-contained subframestructure. A subframe is configured in an order of a resource sectionfor downlink, a resource section for data, and a resource section foruplink and a GP exists prior to the resource section for uplink only. InFIG. 5(b), a downlink resource section represented as DL may correspondto a resource section for a downlink control channel and an uplinkresource section represented as UL may correspond to a resource sectionfor an uplink control channel.

The next generation 5G system is considering V2X targeting ultra-lowlatency, eMBB service targeting emergency service, machine control, anddata speed, and the like. Hence, it is necessary to design a framestructure capable of supporting low latency (OTA<1 ms) and high degreeof freedom of DL/UL data. And, it is necessary to design acommonality-based single frame structure which is not necessary to beredesigned in TDD or FDD operation scheme.

In order to provide the low latency and the degree of freedom of DL/ULdata configuration in the next generation 5G system, the presentinvention proposes a method of configuring a new frame structure and acontrol zone. In the present specification, such a term as a zoneindicates a resource. Such a terms as a region, a channel, and the likecan be used together with the zone in the same meaning.

Proposal 1: New Frame Structure (Adaptive/Self-contained FrameStructure) for 5G Systems

It is difficult to satisfy a requirement of OTA<1 ms in a currentLTE/LTE-A TDD frame structure. And, although TDD scheme provides variousTDD DL/UL configurations to efficiently support asymmetry (DL traffic>ULtraffic) of DL/UL data amount, it causes a complex procedure for HARQ(hybrid automatic repeat request) ACK/NACK time depending on a TDD DL/ULconfiguration. In order to solve the problem, as shown in FIG. 5,self-contained frame structures provide an opportunity for transmittingACK/NACK in every subframe by simultaneously configuring a DL controlzone (or, a DL control channel, a DL control region) and an UL controlzone in a single subframe.

FIG. 6 is a diagram for a HARQ procedure when a UL resource of a datazone is immediately allocated.

When a data zone is always guaranteed as an UL data zone or a DL datazone (or, DL data region) based on the subframe structure shown in FIG.5(b), it may be able to perform a HARQ procedure within 5 subframesbetween OTA (w/initiation), i.e., UL buffer arrival, and final ACK/NACKreception.

FIG. 6 illustrates an example that HARQ ACK is received within 5subframes. A corresponding procedure is described in the following.Subframe #1: if a data to be transmitted in UL is generated and a bufferarrival event is triggered, a UE transmits a scheduling request (SR)using an UL control zone. A subframe #2 corresponds to time forperforming UL scheduling. A subframe #3 corresponds to a DL controlzone. The UE receives a UL grant and prepares data to be transmitted inthe subframe #3. The UE transmits UL data via a data zone in a subframe#4. A subframe #5 corresponds to time for a base station to receive dataand perform Rx processing. The UE receives ACK via a DL control channelin a subframe #6.

According to the abovementioned procedure, from the timing at which thebuffer arrival event occurred to the timing at which the ACK isreceived, it is able to see that the procedure occurs within 5subframes. Hence, if TTI is configured by 0.2 ms, ‘OTA (w/initiation)<1ms’ is satisfied. However, since a data zone is restricted to a UL datazone or a DL data zone in a single subframe, if DL (or UL) trafficconsiderably occurs, as shown in FIG. 7, it is apparent that a case offailing to transmit DL (or UL) traffic occurs.

FIG. 7 is a diagram for a HARQ procedure when a UL resource of a datazone is not immediately allocated.

As shown in FIG. 7, if it fails to perform scheduling on UL data due toDL traffic for other UEs in a fourth subframe form the left side,latency as much as 1 subframe occurs and it is unable to satisfy ‘OTA(w/initiation)<1 ms’. Moreover, if it is necessary to transmit more DLtraffic, the latency is going to be extended. In particular, in order toachieve not only asymmetry of DL/UL traffic amount but also low latency,it is necessary to guarantee the degree of freedom of DL/UL traffic asmuch as possible in a data zone.

The present invention proposes a new frame structure capable ofsatisfying low latency and DL/UL data flexibility on the basis of asingle carrier.

Proposal 1-1

FIG. 8 is a diagram for a new frame structure according to a proposal1-1 of the present invention.

As shown in FIG. 8, a subframe is mainly divided into a DL control zone(or DL control channel), a GP, a data zone (data region or datachannel), and a UL control zone (or UL control channel) on a singlecarrier. A frame structure shown in FIG. 8 corresponds to a framestructure which is configured under the assumption that a base stationoperates in a full duplex radio (FDR) scheme. Meanwhile, the framestructure shown in FIG. 8 may correspond to a frame structure allocatedby a base station for a single UE. For example, if the frame structureshown in FIG. 8 corresponds to a frame structure allocated by a basestation for a single UE, a DL data zone, a UL data zone, and a UL datazone are allocated to the UE according to a band in frequency domaindirection in a first subframe shown in FIG. 8. In this case, the UEreceives DL data from the base station on a band represented by DL andtransmits UL data to the base station on a band represented by UL. Inparticular, the frame structure shown in FIG. 8 may correspond to aframe structure allocated to the UE under the assumption that the UE isable to operate in the FUR as well.

In FIG. 8, the DL data zone and the UL data zone, which are allocatedaccording to a band in a subframe, can be differently configuredaccording to a subframe. For example, referring to FIG. 8, a DL datazone, a UL data zone, and a UL data zone can be allocated according to aband in frequency domain direction in a second subframe.

As shown in FIG. 8, a DL control zone is located at the first (start) ofa subframe in time domain, a data zone (a zone represented by DL, UL) islocated right after the DL control zone, and a UL control zone is lastlylocated after the data zone. In this case, the data zone can be used asa DL data or a UL data in frequency domain without any restriction. And,a GP is located between the DL control zone and the data zone when databelonging to a corresponding band corresponds to UL. On the contrary,when data corresponds to DL, a GP is located between the data zone andthe UL control zone.

As shown in FIG. 8, a UL transmission occasion and a DL transmissionoccasion exist at the same time in a data zone in every subframe. Inparticular, it is able to prevent additional latency due to therestriction of a legacy data zone restricted to DL or UL. If a length ofa subframe is configured to be equal to or less than 0.2 ms, it is ableto achieve ‘OTA (w/initiation)<1 ms’.

Moreover, a base station may have more efficiency via DL/UL flexibilityof the data zone in the aspect of utilizing DL/UL data resource comparedto a legacy self-contained TDD frame structure. Hence, the framestructure shown in FIG. 8 is able to get rid of inefficiency due to theasymmetry of DL/UL traffic and achieve low latency.

Embodiment of Proposal 1-1

Embodiment for a method of achieving low latency and an operating methodwhen DL data transmission timing is overlapped with UL data transmissiontiming are described in the following.

FIG. 9 is a diagram for explaining a case that DL transmission timing isoverlapped with UL transmission timing.

As shown in FIG. 9, when a DL buffer arrival event and a DL bufferarrival event respectively occur, one of the two buffer arrival eventshas no choice but to be delayed in a legacy frame structure. In FIG. 9,it is assumed that 2 traffics (DL traffic and UL traffic) areoverlapped. If more traffic occurs at the same time, more latency mayoccur.

On the other hand, referring to a frame structure shown in FIG. 9, sincea DL data zone and a UL data zone are allocated within a subframe, it isable to transmit DL data and UL data at the same time and simultaneoustransmission is also supported while minimum latency is maintained. Theframe structure shown in FIG. 9 has a merit in that a gain increasesaccording to the increase of traffic.

Proposal 1-2

A DL control zone and a UL control zone can be configured by 1 to Nnumber of symbols. A GP is configured by an integer multiple of asymbol. More specifically, a length of a GP can be configured by aninteger multiple of a unit symbol allocated to a data zone.

In general, a length of a GP is designed by a round trip time (RTT) andRF switching time (from DL to UL/from UL to DL). Hence, the length ofthe GP can be determined by a method of minimizing overhead inconsideration of RTT and RF switching time overhead (e.g., aself-contained frame structure).

If the frame structure shown in FIG. 8 corresponds to a frame structureallocated by a base station for a plurality of UEs, the base stationoperates in a full duplex scheme that performs UL/DL data transmissionand reception at the same time in a data zone. On the contrary, The UEsoperate in a half-duplex scheme that performs either transmission orreception only. Hence, it is necessary for the base station to transmitDL data and receive UL data at the same time. In this case, if GPs areconfigured according to a legacy method, as shown in FIG. 10, it isapparent that interference occurs due to the mismatch between symbolboundaries.

FIG. 10 is a diagram illustrating an example that a DL data symbolboundary is not matched with a UL data symbol boundary in a data zone ina base station.

A base station receives data transmitted in DL within in-band. Hence, ifa level of the mismatch is less than a CP length, it is able to receiveUL data without interference on an ideal channel via orthogonality ofOFDM. Yet, as shown in FIG. 10, a GP makes a symbol boundary between ULdata and DL data to be mismatched. Hence, as shown in FIG. 8, it may beable to cancel the interference by configuring a GP length of a datazone by a symbol length.

In particular, the GP length of the data zone is configured to satisfyequation 1 in the following all the time by making the GP length to bean integer multiple of a length of a unit symbol that constructs thedata zone.

Length of data zone÷Number of symbols in data zone=Length of singlesymbol=T_cp+T_u=GP length÷k  [Equation 1]

In this case, k is a natural number, T_cp corresponds to a CP length,and T_u corresponds to a length of a data part in a symbol. Inparticular, a length of a GP becomes an integer multiple of a length ofa unit symbol that constructs a data zone.

And, a DL control zone and a UL control zone can be configured by Nnumber of symbols without being restricted to a single symbol.

The frame structure shown in FIG. 10 requires a transceiver configuredto perform DL and UL (i.e., transmission and reception) at the same timein a DL zone. A structure of the transceiver can be configured asfollows.

FIG. 11 is a diagram illustrating an example of an RF structure of atransceiver of a base station.

FIG. 11 illustrates configurations of devices for performingtransmission and reception at the same time in a single carrier. Firstof all, in order to reduce power leakage that a signal transmitted by abase station is entering a receiving end, a signal is attenuated using acirculator. In addition, it may be able to additionally suppress aself-interference signal via an analog SIC device.

The frame structure proposed in the proposal 1 has the characteristicthat transmission occasion of DL/UL traffic of FDD is always guaranteedin a legacy system. The frame structure can also efficiently use aresource according to asymmetry of DL/UL traffic of TDD.

In the following, a frame structure of a base station and a UE operatingin a TDD or FDD mode is proposed.

Proposal 2-1

In a TDD carrier, a subframe is mainly divided into a DL control zone, aGP, a data zone, and a UL control zone. The DL control zone is locatedat the first of the subframe, the data zone is located right after theDL control zone, and the UL control zone is lastly located after thedata zone. In this case, the data zone can be used as a DL data or a ULdata in the subframe. And, a GP is located between the DL control zoneand the data zone when data belonging to a corresponding bandcorresponds to UL. On the contrary, when data corresponds to DL data, aGP is located between the data zone and the UL control zone. The DLcontrol zone and the UL control zone can be configured by 1 to N numberof symbols. A GP is configured by an integer multiple of a symbol.

FIG. 12 is a diagram illustrating an example of a frame structuretime-frequency resource on a TDD carrier.

As shown in FIG. 12, a data zone of every subframe is allocated as a ULdata zone or a DL data zone. Hence, DL/UL flexibility is loweredcompared to the frame structure of the proposal 1. Yet, since the DLcontrol zone and the UL control zone are still located within a singlesubframe, ‘OTA (w/initiation)<1 ms’ can be achieved by a scheduler.Moreover, since it is able to utilize the data zone as a DL data zone ora UL data zone by the scheduler, it is apparent that the frame structureis more DL/UL flexible compared to the legacy LTE TDD.

A length of a GP is configured by a multiple of a symbol length. Thismakes numerology (subcarrier spacing, CP length, symbol length, numberof symbols in a TTI) used in TDD to be identically used in a FDD framestructure. In particular, it is a design method for providingcommonality as much as possible in the TDD and FDD frame structures. Asa result, it may be able to maintain a lot of common parts in a basebandoperation.

For example, when a GP is designed by a length of half symbol withoutbeing maintained by the length of one symbol, if the same TTI isapplied, the number of symbols or a CP length varies in TDD and FDD andit breaks unity in terms of an implementation device. As a result, itmay implement TDD and FDD, respectively. On the contrary, if a GP lengthis maintained by a multiple of a symbol length, since it is able tocommonly use a CP, a symbol length, and the like, it may have anadvantage that a commonly used implementation part increases.

Proposal 2-2

FIG. 13 is a diagram illustrating an example of a frame structuretime-frequency resource on a FDD carrier.

In FIG. 13, a subframe is mainly divided into a control zone and a datazone on a FDD carrier. In case of DL, the control zone is located at thefirst of the subframe and the data zone is located after the controlzone. In case of UL, a UL control zone is located at the first of thesubframe and the data zone is located after the UL control zone.

FIG. 13 illustrates a frame structure that a GP is utilized as a dataand a control zone is located at the first part of a subframe in alegacy TDD frame structure. As mentioned in the foregoing description,commonality is maximized by maintaining a common part with the legacyTDD frame structure as much as possible.

As mentioned in the foregoing description, the frame structure accordingto the proposal provided by the present invention can achieve lowlatency (i.e., OTA (w/initiation)<1 ms) corresponding to 5G servicerequirement and provide DL/UL flexibility capable of efficientlysupporting asymmetry of DL/UL traffic as much as possible.

In order to support mobility 500 Km/h corresponding to 5G New RAT systemrequirement in a self-contained subframe structure, subcarrier spacingincreases and TTI decreases to achieve low latency (i.e., OTA(w/initiation)<1 ms) corresponding to 5G service requirement. Forexample, assume that the subcarrier spacing increases to 75 kHz and theTTI decreases to 0.2 ms. Then, coherence time is reduced to (Tc=1/(2fd)≈0.18 ms and the coherence time is maintained by a single referencesymbol (hereinafter, RS) within 0.2 ms TTI. On the contrary, sincemaximum r.m.s channel delay spread is maintained by 991 ns and acoherence bandwidth is maintained by (Bc_90%=20 kHz, Bc_50%)=200 kHz,spacing between two RSs should be maintained by 90 kH.

Hence, it is necessary to allocate an RS to the whole band to estimate achannel. In particular, it is necessary to allocate an RS fordemodulating a control channel to the whole band of a resource to whichthe control channel is assigned. And, it is necessary to allocate an RSfor demodulating a data channel to the whole band of a resource to whichthe control channel is assigned. Or, if a specific band is scheduledonly, the RS can be allocated to a specific band only.

A self-contained subframe includes 3 channels (a DL control channel, adata channel, and a UL control channel) in total. It is necessary toallocate RSs for the 3 channels. In this case, the RSs can be allocatedto at least 3 or more symbols. If it is assumed that the self-containedsubframe is configured by 14 symbols in total, since RSs are allocatedto 3 or more symbols for the 3 channels, resource overhead of 3/14occurs. Hence, it is necessary to have a method of improving theresource overhead.

Proposal 3: Method of Reducing RS Overhead in Self-contained SubframeStructure

As a solution for the proposal 3, the present invention proposes amethod of using RSs for estimating or demodulating a control channel anda data channel in the same resource region in a manner of overlappingthe RSs in the resource region.

FIG. 14a is a diagram for an example of an RS assignment pattern when aresource region for DL/UL flexibility is allocated via a DL data channelin a self-contained subframe and FIG. 14b is a diagram for an example ofan RS assignment pattern when a resource region for DL/UL flexibility isallocated via a UL data channel in a self-contained subframe.

FIG. 14a illustrates a frame structure when a data region corresponds toa DL data region. FIG. 14b illustrates a frame structure when a dataregion corresponds to a UL data region.

Referring to FIG. 14a , a first symbol and a second symbol of a subframecan be configured as a DL control region. And, an RS for coherentlydemodulating DL control information can be assigned to the first symbol.In this case, the RS for coherently demodulating the DL controlinformation (or a control channel) and an RS for coherently demodulatingDL data are mapped to the first symbol in a manner of being overlapped.And, the last symbol of the subframe is assigned as a UL control regionand an RS for coherently demodulating UL control information (or a ULcontrol channel) is located after a GP.

As shown in FIG. 14b , if a data region is allocated as a UL dataregion, an RS for coherently demodulating DL control information islocated at the first symbol of a subframe in a DL control region and anRS for UL data and an RS for UL control information are overlapped atthe first part of the UL data region after a GP. FIG. 14b shows anexample that an RS for UL data and an RS for UL control information aremapped to a fourth symbol of a subframe in a manner of being overlapped.The RS assignment shown in FIGS. 14a and 14b can reduce RS resourceoverhead by half compared to a method of making RSs to be located at thecontrol region and the data region, respectively.

In FIGS. 14a and 14b , although RS patterns are overlapped with eachother at the first symbol, by which the present invention may benon-limited. For example, as shown in FIGS. 15a and 15b , overlap isavailable for various patterns and an RS overlap mapping technology isnot limited by an RS assignment pattern.

FIG. 15a is a diagram for an example of an RS assignment pattern when aresource region for DL/UL flexibility is allocated via a DL data channelin a self-contained subframe and FIG. 15b is a diagram for an example ofan RS assignment pattern when a resource region for DL/UL flexibility isallocated via a UL data channel in a self-contained subframe.

Referring to FIG. 15a , an RS for coherently demodulating DL controlinformation and DL data can be assigned to a first symbol and a secondsymbol of a subframe assigned as a DL control region and an RS forcoherently demodulating UL control information can be assigned to thelast two symbols of a subframe assigned as an UL control region.Referring to FIG. 15b , an RS for coherently demodulating DL controlinformation can be assigned to a first symbol and a second symbol of asubframe assigned as a DL control region and an RS for coherentlydemodulating UL control information and UL data can be assigned to twosymbols appearing after a GP.

Moreover, a position of an RS in time domain can be arranged in a mannerof being distributed to all time domains of data and controlinformation. In this case, delay may occur when the control informationis demodulated.

A procedure for a UE and an eNB to demodulate control information anddata is described in the following. First of all, for clarity, an RS forcontrol information and an RS for data are defined as C_RS and D_RS,respectively.

As Shown in FIGS. 14a and 15a , When Data Region is Assigned as DL DataRegion (DL Control and DL Data)

eNB Operation

First of all, RE mapping is performed in a manner of generating controlinformation entering into a control channel and C_RS for demodulation.In this case, the C_RS is mapped to an overlapped RS region. After DLdata and D_RS for demodulating the DL data are generated, data is mappedto a resource region (or resource block) designated by DL controlinformation. And, the D-RS and a C_RS for a control channel aretransmitted to a UE in a manner of being overlapped in an overlapped RSregion corresponding to the same frequency domain.

UE Operation

In order to detect DL control information, a UE estimates a channel inan overlapped RS region using C_RS and may be then able to obtain the DLcontrol information using the estimated channel. The UE is able to knowwhether or not there exist data assigned to the UE based on the obtainedDL control information. If there exists data assigned to the UE, the UEperforms channel estimation in the overlapped RS region using D_RS for acorresponding frequency domain position. The UE can detect the dataassigned to the UE based on the channel estimation using the D_RS.

As Shown in FIGS. 14b and 15b , When Data Region is Assigned as UL DataRegion (UL Data and Control)

UE Operation

First of all, assume that an eNB implicitly or explicitly allocates a ULdata region and a UL control region to each UE. If both UL data regionand UL control region are assigned to a UE, the UE generates data andD_RS, maps the data to an allocated DL data resource region, and mapsthe D_RS to an overlapped region.

And, the UE generates UL control information and C_RS, maps the ULcontrol information to a UL control region, and maps the C_RS to anoverlapped RS region in a manner of overlapping the C_RS with the D-RS.

When UL data is assigned to the UE only, if data is transmitted only,the UE generates D_RS and maps the D_RS to an overlapped RS regionassigned to the UE. On the contrary, when UL control information isassigned to the UE only, the UE maps the C-RS to an overlapped RS regioncorresponding to a region assigned to the UE.

eNB Operation

In order to detect UL control information and UL data of UEs, an eNBperforms channel estimation based on C-RS or D_RS at a preassignedposition.

When C_RS and D_RS are used in a manner of being overlapped in the sameRS region, it is important to secure orthogonality between the RSs interms of performance. A sequence can be configured in various ways usingan orthogonal cover code (OCC), cyclic shift, or the like.

FIG. 16 is a diagram for a method of securing orthogonality between C_RSand D_RS when a data region is allocated to a DL data region in aself-contained subframe structure.

Referring to FIG. 16, two D_RSs (e.g., dual layer (D-RS #1 and D_RS #2))are assigned to an RB (resource block) #1 and one D_RS is assigned to anRB #2. The total 3 RSs (i.e., C_RS, D_RS #1, and D_RS #2) are mapped infrequency domain of the RB #1 in a manner of being overlapped. In orderto secure orthogonality for reception capability, sequences applied tothe RSs can be configured to have orthogonal characteristic. Forexample, if a cyclic shift value is differently configured according toeach RS on the basis of a base sequence, it may be able to secureorthogonality in time domain. As a different method, it may be able tosecure orthogonality in frequency domain by assigning sequencesdifferent from each other that maintain orthogonality in frequencydomain.

It may also be able to configure the RB #2 using a cyclic shift or anOCC to secure orthogonality between the C_RS and the D_RS #1. A UE candetect C_RS-based DL control information based on the orthogonality anddetect DL data using corresponding D_RS to detect a resource allocatedto the UE.

In this case, the number of overlapped RSs may vary depending on thenumber of layers of actually allocated RBs. And, a length unit of an RScan be extended to a plurality of RBs. In the following, a method ofsecuring orthogonality using a cyclic shift value is explained withreference to FIG. 17 among the methods of securing orthogonality.

FIG. 17 is a diagram for explaining a case that a control channel isused for the whole band and a data channel is used for 24^(th) RB and2^(nd) RB among 25 RBs in total.

C_RS can be transmitted on the whole band of a resource to which a DLcontrol channel is assigned. D_RS is mapped to a region to which theC_RS is mapped. The D_RS and the C_RS can be overlapped and mapped to aregion to which DL data is assigned only (In FIGS. 17, 2^(nd) and24^(th) RBs only).

FIG. 17 shows a method of configuring a sequence using a base sequenceand cyclic shift (CS) according to an RB. For clarity, assume that abase sequence to which CS is to be applied and a sequence to which acyclic shift value m is applied are defined as b₀ and b_(0,m) ,respectively. And, assume that a symbol length and the number ofsubcarriers per RB correspond to N_(sym) and N_(SC), respectively.Hence, it may be able to secure orthogonality in time domain in a mannerof applying a CS values ranging from 0 to maximum N_(SC)-1.

As shown in FIG. 17, a base sequence b0 is applied to all RBs of C_RSand a CS value as much as 6 is applied to an RB index 24 and an RB index2 to which data is assigned. The C_RS for demodulating a DL controlchannel can estimate a channel using a base sequence. In particular,since a channel impulse response is located at a part corresponding to afirst 1/N_(SC) of the total symbol length N_(sym) in time domain inevery RB, it may be able to estimate a DL control channel using thepart.

If a UE is able to know positions of assigned data through a DL controlchannel and the positions correspond to an RB index 2 and an RB index24, since a channel impulse response is located at a part correspondingto 6/N_(SC)˜7/N_(SC) of the total symbol length N_(sym) in time domain,the UE is able to estimate a data channel using the part.

In this case, a size of a time window and an applied CS value (i.e., 6)can be applied using various values. For example, if the CS value isrestricted to values including 0, 2, 4, . . . , N_(SC)-2, a region atwhich a channel impulse response is located can be increased to2N_(sym)/N_(SC). And, a configuration of the value can be determinedaccording to a channel delay spread value. And, when a channel delayspread value is big, if a value farthest from a base value 0 is selectedas a CS value, it may be able to prevent a channel impulse response frombeing overlapped.

Hence, an eNB can inform a UE of a unit of increasing a CS value throughhigher layer signaling (e.g., RRC signal). And, the eNB can transmit aCS value applied to data to the UE in a manner of including the CS valuein DCI (downlink control information). And, the method can also beextensively applied to RBG (resource block group).

As a method of determining a cyclic shift value, a CS value of C_RS anda CS value of D_RS can be configured to have a maximum space.Simultaneously, a space between C_RSs and a space between D_RSs can beconfigured to have a maximum space to more secure orthogonality.

Table 1 in the following shows an example when an RB reference N_(SC)corresponds to 12.

TABLE 1 # of layers of # of layers of C_RS (or # of D_RS (or # of CSvalues for antenna ports) antenna ports) C_RS CS values for D_RS 1 1 0 61 2 0 {4, 8} 1 4 0 {4, 6, 8, 10} 2 2 {0, 6} {3, 9} 2 4 {0, 6} {2, 4, 8,10} 4 1 {0, 2, 4, 8} 10 4 2 {0, 2, 6, 10} {4, 8} 4 8 {0, 3, 6, 9} {1, 2,4, 5, 7, 8, 10, 11}

As a method of determining a base sequence applied to C_RS and D_RS, abase sequence can be determined based on a cell ID or a subframe indexto randomize inter-cell interference. UL data can also be configured bya method identical to a method of configuring DL data.

According to one embodiment of the present invention, it is able toreduce waste of an RS resource for detecting a data channel and acontrol channel in a self-contained frame structure and reduce decodinglatency.

The above-described embodiments correspond to combinations of elementsand features of the present invention in prescribed forms. And, therespective elements or features may be considered as selective unlessthey are explicitly mentioned. Each of the elements or features can beimplemented in a form failing to be combined with other elements orfeatures. Moreover, it is able to implement an embodiment of the presentinvention by combining elements and/or features together in part. Asequence of operations explained for each embodiment of the presentinvention can be modified. Some configurations or features of oneembodiment can be included in another embodiment or can be substitutedfor corresponding configurations or features of another embodiment. And,it is apparently understandable that an embodiment is configured bycombining claims failing to have relation of explicit citation in theappended claims together or can be included as new claims by amendmentafter filing an application.

Those skilled in the art will appreciate that the present invention maybe carried out in other specific ways than those set forth hereinwithout departing from the spirit and essential characteristics of thepresent invention. The above embodiments are therefore to be construedin all aspects as illustrative and not restrictive. The scope of theinvention should be determined by the appended claims and their legalequivalents, not by the above description, and all changes coming withinthe meaning and equivalency range of the appended claims are intended tobe embraced therein.

INDUSTRIAL APPLICABILITY

A method of transmitting and receiving a reference signal in a wirelesscommunication system and an apparatus therefor can be applied to variouswireless communication systems including 3GPP LTE/LTE-A, 5G system, andthe like.

What is claimed is:
 1. A method for transmitting a reference signal by atransmitting side in a wireless communication system, the methodcomprising: generating first reference signals for demodulating acontrol channel and second reference signals for demodulating a datachannel; mapping the first reference signals and the second referencesignals to a resource of a predefined subframe to which the controlchannel is assigned by overlapping the first reference signals and thesecond reference signals; and transmitting the first reference signalsand the second reference signals mapped to the resource to which thecontrol channel is assigned.
 2. The method of claim 1, whereinpredefined cyclic shift values are applied to the first referencesignals and the second reference signals.
 3. The method of claim 2,wherein different cyclic shift values are applied to the first referencesignals and the second reference signals.
 4. The method of claim 1,wherein when two values have a greatest difference in predefined cyclicshift values, one of the two values is applied to the first referencesignals and another is applied to the second reference signals.
 5. Themethod of claim 1, wherein the resource to which the control channel isassigned comprises a first symbol, a second symbol, a fourth symbol, ora immediately preceding symbol of a last symbol in the predefinedsubframe.
 6. The method of claim 1, wherein the mapping furthercomprises mapping the first reference signals and the second referencesignals to whole band of the resource to which the control channel isassigned.
 7. A method for receiving a reference signal by a receivingside in a wireless communication system, the method comprising:receiving first reference signals for demodulating a control channel andsecond reference signals for demodulating a data channel in a resourceto which a control channel is assigned; detecting control informationusing the first reference signals; and detecting data using the controlinformation and the second reference signals.
 8. The method of claim 7,wherein the first reference signals and the second reference signals arereceived in a manner of being overlapped and mapped to the resource of apredefined subframe to which the control channel is assigned.
 9. Themethod of claim 7, wherein the first reference signals and the secondreference signals are received in a manner of being mapped to a wholeband of the resource to which the control channel is assigned.
 10. Themethod of claim 7, wherein predefined cyclic shift values are applied tothe first reference signals and the second reference signals.
 11. Themethod of claim 10, wherein different cyclic shift values are applied tothe first reference signals and the second reference signals.
 12. Themethod of claim 7, wherein when two values have a greatest differenceamong predefined cyclic shift values, one of the two values is appliedto the first reference signals and another is applied to the secondreference signals.
 13. The method of claim 7, wherein the resource towhich the control channel is assigned comprises a first symbol, a secondsymbol, a fourth symbol, or a immediately preceding symbol of a lastsymbol in the predefined subframe.
 14. A transmitting apparatus fortransmitting a reference signal in a wireless communication system,comprising: a processor configured to generate first reference signalsfor demodulating a control channel and second reference signals fordemodulating a data channel, the processor configured to map the firstreference signals and the second reference signals to a resource of apredefined subframe to which the control channel is assigned byoverlapping the first reference signals and the second referencesignals; and a transmitter configured to transmit the first referencesignals and the second reference signals mapped to the resource to whichthe control channel is assigned.
 15. A receiving apparatus for receivinga reference signal in a wireless communication system, comprising: areceiver configured to receive first reference signals for demodulatinga control channel and second reference signals for demodulating a datachannel in a resource to which a control channel is assigned; and aprocessor configured to detect control information using the firstreference signals, the processor configured to detect data using thecontrol information and the second reference signals.